The use of high-power fiber-coupled lasers continues to gain popularity for a variety of applications, such as materials processing, cutting, welding, and/or additive manufacturing. These lasers include, for example, fiber lasers, disk lasers, diode lasers, diode-pumped solid state lasers, and lamp-pumped solid state lasers. In these systems, optical power is delivered from the laser to a work piece via an optical fiber. Low power lasers are also employed in many applications, including, for example, medical systems and procedures, measurement and detection devices, communication systems and so forth.
Various fiber-coupled laser materials processing tasks require different beam characteristics (e.g., spatial profiles and/or divergence profiles). For example, cutting thick metal and welding generally require a larger spot size than cutting thin metal. Ideally, the laser beam properties would be adjustable to enable optimized processing for these different tasks. Conventionally, users have two choices: (1) Employ a laser system with fixed beam characteristics that can be used for different tasks but is not optimal for most of them (i.e., a compromise between performance and flexibility); or (2) Purchase a laser system or accessories that offer variable beam characteristics but that add significant cost, size, weight, complexity, and perhaps performance degradation (e.g., optical loss) or reliability degradation (e.g., reduced robustness or up-time). Currently available laser systems capable of varying beam characteristics require the use of free-space optics or other complex and expensive add-on mechanisms (e.g., zoom lenses, mirrors, translatable or motorized lenses, combiners, etc.) in order to vary beam characteristics. No solution exists that provides the desired adjustability in beam characteristics that minimizes or eliminates reliance on the use of free-space optics or other extra components that add significant penalties in terms of cost, complexity, performance, and/or reliability. What is needed is an in-fiber apparatus for providing varying beam characteristics that does not require or minimizes the use of free-space optics and that can avoid significant cost, complexity, performance tradeoffs, and/or reliability degradation.
Further, controlling directional characteristics, spatial properties and divergence properties for laser beams can be useful in many applications. Current systems for controlling directional characteristics, spatial properties and/or divergence of an optical beam often include adjustable free-space optics, such as mirrors or lenses. The movement of these free-space optics relative to the laser beam can be mechanically controlled in order to control direction and/or divergence. However, such mechanical systems add complexity, cost and sensitivity to environmental conditions (e.g., temperature and vibration) and contamination.
End caps are sometimes employed at the end of optical fiber lasers to protect the fiber end from damage. However, these end caps are generally designed so as to have an end face that is normal to the optical axis of the fiber when positioned on the fiber, so as not to significantly modify a laser beam being emitted from the end cap. The end caps are manufactured within tolerances, so that the beam direction characteristics are not modified by, for instance, more than 10 milliradians.